Q&A site Quora is rewarding its top writers with a welcome package that includes a t-shirt and a Best of Quora 2010-2012 book. You don't have to be a Quora top writer, though, to read that book yourself, since this 400-page tome is now available as a free PDF download for everyone.

The book covers 18 different categories, everything from food to life advice and science. More than 100 questions are answered here, from the simply interesting ("What is it like to be a contestant on Jeopardy?") to the practical ("How does a star engineering high school student choose amongst MIT, Caltech, Stanford, and Harvard?" and "My kids have started learning chess. Is it a good idea to let them beat me sometimes to encourage them?"—the latter question answered by Wikipedia founder Jimmy Wales.)